1. Field of the Invention
The present general inventive concept relates to an inkjet image forming apparatus, and more particularly, to an inkjet image forming apparatus including an array type inkjet head.
2. Description of the Related Art
In general, inkjet image forming apparatuses are apparatuses that form images by injecting ink onto sheets of paper conveyed in a sub-scanning direction from an inkjet head, which reciprocates in a main scanning direction (shuttle type inkjet head). Recently, the printing operation is also being performed at a high speed using an inkjet head (array inkjet head) including a nozzle portion having a length of a main scanning direction corresponding to a width of the paper instead of using the shuttle type inkjet head. In the inkjet image forming apparatus, the inkjet head is fixed, and the sheets of paper are conveyed in a sub-scanning direction. Therefore, a driving unit for the inkjet image forming apparatus has a simple structure, and the printing operation can be performed at a high speed.
The inkjet head includes a nozzle portion including a plurality of nozzles, through which ink is injected. When the nozzle portion is exposed to air during a time in which the printing operation is not performed, humidity in the ink is evaporated and the viscosity of the ink increases. Also when the nozzle is not being used to perform the printing operation, humidity in the ink is evaporated and viscosity of the ink increases. Therefore, a defective injecting operation may occur due to the ink having a high viscosity. Thus, a preliminary spitting operation is performed in order to remove the ink having high viscosity.
However, in the array type inkjet head, thousands of nozzles are formed, and thus, a large amount of ink is preliminarily spitted. Therefore, the waste ink from the spitting should be pumped into a waste ink container.